We reported previously that several mutations that abolish either of the two mechanisms of replication repair are general mutator mutations that sometimes promote templated mutations particularly strongly. Thus, defects in replication repair somehow promote template switching to an inappropriate template. We are now pursuing hypotheses making predictions about the properties of mutants carrying mutational blocks either in both pathways, or in both steps of one of the pathways. We are also testing whether each component of an imperfect reverse repeat can template mutations in the other component.